When combating wildfire from the air, various tools can be utilized. One common tool is to load an appropriately configured aircraft with wildland fire chemicals, fly the aircraft over the fire or an area adjacent the fire to be protected, and discharge the fire chemical from the aircraft. While such fire chemicals are quite effective in suppressing wildfire, the aircraft must travel to a reloading base and return to the location of the wildfire before additional loads can be dropped, decreasing the effectiveness of such aircraft proportional to the distance the reloading base is from the fire and the time such reloading takes.
In many instances bodies of water are available in the area where the wildfire is occurring. Helicopters can be utilized with buckets suspended therefrom (or fixed tanks and snorkel pumps) which can be loaded with water and then flown to the site of the wildfire and discharged. Water is not as effective as fire retardants or suppressants in combating wildfire. Also, helicopters have a lesser payload capacity than airplanes.
It is also known to utilize airplanes for dropping water onto wildfires. Such airplanes are configured to skim over a body of water to load tanks therein with water. Such airplanes then fly to the site of the fire where the water can be released.
Water's effectiveness as a fire suppressant can be significantly enhanced by adding a suppressant polymer to the water. One such polymer material is provided under the trademarks FIREWALL ULTRA, provided by BroadRange Wildland Fire Chemicals of Cold Springs, Calif. and FIREWALL II, provided by Eco FireSolutions of Carmichael, Calif. One unique characteristic of such polymer material is that merely adding the polymer material to water does not provide the full benefit of fire suppressant capacity to the water. Rather, the polymer must be both activated and thoroughly mixed with the water. Shearing forces cause the water to have the polymer fully activated as a first part of the polymer preparation process, so that the fire suppressant effect of the water can be maximized. A second part of the preparation process is mixing to distribute the activated polymer throughout the water load. A pump is typically used which provides the required shearing/mixing force to activate the polymer.
While it would be desirable to add polymer to water in a fire fighting aircraft, complexities associated with the required mixing to impart the highest fire suppressant effect on the water polymer mixture, requires appropriate polymer mixing equipment. Such equipment requires a relatively large amount of power and has significant weight. When a firefighting aircraft is being outfitted for firefighting, it is desirable that as much of the available payload capacity of the aircraft be utilized for carrying water and polymer, as possible. Known pumping equipment burdens the aircraft with extra weight thus minimizing effectiveness. Accordingly, a need exists for methods to mix polymer with water (and ongoing mixing as well up until discharge) with minimal equipment needed for polymer and water preparation before drop.
In some instances a fire fighting aircraft may benefit from first taking on a load of water and later, at the option of the operator, having polymer gel emulsion added to the water within the tank and activated and mixed with the water shortly before the water and polymer gel emulsion are to be dropped. With such a delayed addition of polymer gel emulsion to water within the tank, along with activation and mixing thereof, an operator has the opportunity to take on a load of water in a first step and not have the polymer gel emulsion immediately added thereto. Then, should the load of water not be needed for firefighting, the polymer gel emulsion has not been wasted and the water can be dropped without concern for polymer release into the environment. Furthermore, should an operator determine that polymer gel emulsion is not needed, water can be dropped without polymer gel emulsion. Furthermore, an operator can determine shortly before dropping water with polymer gel emulsion how much polymer gel emulsion to add to the water.
Keeping water and activated polymer gel emulsion mixed within a vessel carried by an aircraft is desirable both for fixed wing aircraft and for rotary wing aircraft. With fixed wing aircraft the water and polymer gel emulsion is typically delivered at a firefighting area by opening of doors on a floor of the tank which causes the water and polymer gel emulsion to be dropped from the tank. In the case of rotary wing aircraft, such doors on a bottom of a tank fixed to the underside of the rotary wing aircraft provides one option of discharge. It is also known to utilize a nozzle pointing downwardly from the helicopter or other rotary wing aircraft, as disclosed in U.S. Pat. No. 9,192,797 and co-pending U.S. patent application Ser. No. 14/616,271, filed on Feb. 2, 2015, each incorporated herein by reference in their entireties. Before either type of discharge, it is desirable that the water and polymer gel emulsion maintain a substantially homogenous mixture within the tank. In the case of rotary wing aircraft it is also conceivable that such mixing could be provided within a vessel in the form of a bucket suspended from a rotary wing aircraft with such mixing provided to keep the water and polymer gel emulsion thoroughly mixed before being dumped from the bucket or sprayed through a nozzle carried by the bucket.